While students at an all-girls school in Montgomery County were laboring one day last month to build bridges out of popsicle sticks, their teachers were trying to build bridges for them into the male-dominated field of engineering.

The popsicle-stick bridges shattered under 60 pounds of pressure. Teachers at the Holton-Arms School in Bethesda hope their seemingly unique engineering course will make girls' interest in the field last longer.

"It's about taking risks and getting them over the anxiety of always having to be right all the time," said physics teacher Chris Lee, who designed the course four years ago and wears a tie-dyed lab coat and goatee. The students, who range from sophomores to seniors, study such new technologies as artificial limbs; they research bridge disasters, something Lee guarantees will annoy parents when the teens spout dire predictions during the next family road trip; and they also build bridges and robots.

Lee said that the aim of the course isn't to prepare girls for careers in engineering but simply to get their minds working on physical problem-solving in a way they don't in other subjects. But he's conscious of the imbalance between the sexes in the field he's teaching.

If students do go on to an engineering job, "great," Lee said. "Certainly, the world needs more women engineers."

One December afternoon, weeks of careful work were destroyed in an instant when the students' model bridges shattered under the pressure of a testing device, spraying broken popsicle sticks toward 13 watching classmates. (Another section of the course has about as many students. Holton-Arms has 640 students in grades three through 12.)

"I think I'm getting a heart attack!" said senior Veronica Leonard, 18, as her group's bridge bulged under pressure from the flat testing plate. A pressure gauge ticked digits toward 20 psi, the minimum required by the assignment. Leonard's bridge, which had a roof over a tunnel, made it to 22 before it split into pieces.

Leonard said she plans to follow in the footsteps of her older sister, who after taking the engineering class at Holton-Arms pursued similar courses at Vanderbilt University.

"It seems like such a good applied science," Leonard said.

Advocates for women in engineering said they were unfamiliar with other regular school programs offering pre-college classes targeted at girls, although some girls' schools, such as National Cathedral School in the District, have after-school clubs that make similar efforts. They praised the class, saying that it could be a good way to draw more women to the field.

"The real challenges for reaching out to young women is to get over the stereotype that this isn't something girls do and then to help them build their confidence," said Betty Shanahan, executive director of the Society of Women Engineers, a national group based in Chicago.

About 17 percent of undergraduate engineering degrees were awarded to women in the 2006-07 school year, the latest for which information is available, according to the National Center for Education Statistics. Shanahan said the low numbers of women are holding the field back.

"When you have a diverse team, you bring all kinds of perspectives, approaches, challenges to conventional thinking," she said. "That's particularly valuable when you're in a team that requires creativity and innovation."

Students said they enjoyed the Holton-Arms course in ways they might not at a co-ed school.

"I love the all-girls aspect because you connect with them so well," said sophomore Kelsey Good, 15. "It's such an open environment." She said that she might study environmental engineering in college.

After all the bridges had been destroyed, the students gathered around to watch a slow-motion video of the testing. As individual popsicle sticks gave way, students could see where the bridge failures started.

"Triangles!" Leonard said, explaining the cross-structural supports that had helped other bridges withstand more stress than her own. "We needed more triangles."